Call forwarding method and arrangement for a mobile terminating call

ABSTRACT

A call forwarding method and arrangement for a mobile terminating call, for preventing the taped intermediate announcements that are often made during call forwarding, and which can cause a delay in the call set-up, from possibly causing the time-out of the calling modem or telefax terminal and thus the failure of the call. Information concerning the type of call is transmitted to the mobile exchange handling the call included, for instance, in a message where the subscriber database notifies the carrying-out of call forwarding, and provides a call forwarding number. The mobile exchange implementing the call forwarding checks the type data of the call and omits possible intermediate announcements associated with the call forwarding in case of a data call, but allows intermediate announcements in case of speech calls.

This application claims benefit of International applicationPCT/Fl95/00236 filed May 2, 1995.

FIELD OF THE INVENTION

The present invention relates to a call forwarding method for a mobileterminating call, including the steps of receiving a call, checkingwhether call forwarding is activated for the called subscriber, and, ifit is, starting the activated call forwarding, with which is possiblyassociated an intermediate announcement to the calling subscriber. Theinvention further relates to a mobile communication system arranged foraccomplishing such call forwarding.

BACKGROUND OF THE INVENTION

Present-day mobile communication systems offer subscribers differentdata transmission features in addition to the conventional speechtransmission. The data services of mobile communication systems cangenerally be divided into teleservices and bearer services. A bearerservice is a telecommunication service, which provides signaltransmission between user and network interfaces. For instance, modemservices are bearer services whereas a telephone service and telefaxservice are teleservices. Data services are typically circuit-switched,which means that when using some services, a subscriber makes a call,during which data transmission takes place in the same manner as speechtransmission during a speech call. However, mobile communication systemsare not designed to take into account in all situations whether acircuit-switched connection is used for speech or data transmission butthey handle different types of calls in the same manner, which causesproblems in some situations.

One subscriber facility of the present-day mobile communication systemsis call forwarding, which a subscriber can activate. Call forwarding maybe unconditional call forwarding, a call being thus always forwarded toa given different number than that entered by the calling party. Callforwarding can also be arranged to take place conditionally, forinstance when the subscriber is busy, the subscriber does not answer orthe subscriber is not reached.

Another aspect of the present-day mobile communication systems is that amobile exchange can switch audio-format information to a subscriberduring different phases of a call. Audio information can be divided intoannouncements and audible tones. An announcement is a recorded orsynthesized speech message. An announcement may be chargeable orcharge-free to the calling subscriber. An announcement can also beswitched to the calling subscriber during call set-up, in which case aso-called intermediate announcement is provided. For instance, inconnection with call forwarding, the calling subscriber is informed ofthe forwarding of the call with a special intermediate announcement.Mobile communication network operators want to make this type ofchargeable intermediate announcements of call forwardings, becauseotherwise, the functions of a network would be used free of charge inthis type of situation in cases where neither the calling subscriber northe subscriber of the call forwarding number are in the operator'snetwork.

Intermediate announcements of this type are problematic in connectionwith data calls. Both a modem and a telefax modem wait for an answersignal under time-out control. The time-out of a telefax modemconventionally is 30-40 seconds, and the time-out of a modem is notdefined in standards. The intermediate announcements made in connectionwith call forwarding may cause call set-up time to be prolonged toexceed the determined time limits, as a result of which the calling datamodem or telefax modem assumes that the call attempt has failed anddisconnects the call. As regards data calls, all long intermediateannouncements are problematic, especially in connection with callforwarding on no reply. In addition, modems and telefax terminals can inno manner utilize the announcements, subscribers thus having to pay forunnecessary announcements. The same applies to all other data terminalequipments. The most unfortunate situation is where a subscriber ischarged for a chargeable intermediate announcement, but the call set-upfails due to a delay caused by the intermediate announcement.

Thus, a need exists for preventing intermediate announcements from beingmade in connection with data calls. In the present-day mobilecommunication systems, this need has in no manner been taken intoaccount, and the exchanges making intermediate announcements, forinstance transit exchanges or terminal exchanges, do not at present evenknow the type of a mobile terminating call in connection with callforwarding, and they do not have any facilities for checking the type ofcall and for preventing intermediate announcements in connection withdata calls.

SUMMARY OF THE INVENTION

The object of the present invention is to prevent the failure of thecall set-up of data calls due to intermediate announcements made duringcall forwarding, and to prevent unnecessary intermediate announcements.

This is achieved with the method described in the foregoing BACKGROUNDsection, characterized according to the invention by checking in case ofcall forwarding whether the type of the call is a speech call or a datacall, preventing the intermediate announcement in case of a data call,and allowing the intermediate announcement in case of a speech call.

The invention also relates to an arrangement for carrying out callforwarding in a mobile communication system comprising mobile stations,mobile exchanges and subscriber databases for maintaining user data,such as location data and activated services, in which arrangement amobile exchange is provided with means for making intermediateannouncements to the calling subscriber in connection with carrying outactivated call forwarding. The arrangement is characterized according tothe invention in that the mobile exchange is arranged to check in caseof call forwarding being in an activated state in respect to a callednumber of a subscriber whether the type of the mobile terminating callis a data call or speech call, and to prevent intermediate announcementsto be made in case of data calls, but to allow intermediateannouncements to be made in case of speech calls.

The mobile exchange handling a call is informed of the fact that callforwarding is in an activated state for the called subscriber by somesubscriber database of the network, this database usually also knowingthe type of the call. Alternatively, this information can arrive with acall to be routed from a fixed network. In the preferred embodiment ofthe invention, information concerning the type of the call istransmitted to the mobile exchange as included, for instance, in amessage where the subscriber database notifies the carrying out of callforwarding and gives a number to which the forwarding is to beperformed. The mobile exchange implementing the call forwarding checksthe type data of the call and omits possible intermediate announcementsrelating to the call forwarding in connection with a data call andallows intermediate announcements in connection with speech calls. Themobile exchange implementing the call forwarding may be a transitexchange routing the call or a terminating exchange serving the mobilestation, to which exchange the call is routed.

According to an embodiment of the invention, the call forwarding methodin connection with a terminating exchange comprises the steps ofreceiving a call in a first exchange; performing a routing informationinterrogation to a first database indicated by the directory number ofthe called subscriber; performing a roaming number interrogation fromthe first database to a second database, within the area of which thecalled subscriber is located; transmitting the allocated roaming numberfrom the second database to the first database and further to the firstexchange; routing the call on the basis of the roaming number from thefirst exchange to a second exchange, which serves the area of saidsecond database; observing at the second exchange that the calledsubscriber is busy, not reachable or does not answer; checking in thesecond database whether call forwarding is activated for the subscriber;initiating the activated call forwarding; checking on the basis of theinformation obtained from the second database or in a call set-upmessage whether the call is a speech call or a data call; preventing anintermediate announcement possibly associated with the call forwardingin case of a data call from being made, and; allowing the making of anintermediate announcement possibly associated with the call forwardingin case of a speech call.

According to a second embodiment of the invention, the call forwardingmethod in connection with a transit exchange comprises the steps ofreceiving a call in a first exchange; performing a routing informationinterrogation to a first database indicated by the directory number ofthe called subscriber; observing in the first database that callforwarding is activated for the called subscriber; starting the callforwarding; checking on the basis of the information obtained from thefirst database or in a call set-up message whether the call is a speechcall or a data call; preventing an intermediate announcement possiblyassociated with the call forwarding in case of a data call from beingmade, and; allowing the making of an intermediate announcement possiblyassociated with the call forwarding in case of a speech call.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail by means of the preferredembodiments with reference to the accompanying drawings, in which:

FIG. 1 shows a part of a mobile communication system,

FIG. 2 is a block diagram illustrating the hardware configuration of theGlobal System for Mobile Communications (GSM) system for telefaxtransmission,

FIG. 3 is a block diagram illustrating the hardware configuration of theGSM system for data transmission,

FIG. 4 illustrates a successful call set-up in the GSM system,

FIG. 5 illustrates a call set-up, with which is connected callforwarding, in the GSM system,

FIG. 6 is a block diagram illustrating a mobile exchange operatingaccording to the invention,

FIG. 7 illustrates another call set-up, with which is connected callforwarding, in the GSM system, and

FIG. 8 is a flow diagram for describing the inventive operation of themobile exchange.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention can be used in mobile communication systems inwhich circuit-switched data and speech calls can be established. Theinvention can be used particularly advantageously in the pan-Europeandigital mobile communication system GSM (Global System for MobileCommunications) and in more recently develop mobile communicationssystems of the same type, such as DCS1800 (Digital Communication System)and PCN (Personal Communication Network). In the following, thepreferred embodiment of the invention will be described as implementedin the GSM system, without restricting the invention to it, however.

In FIG. 1, the basic elements of the GSM system will be described verybriefly, without further treatment of their characteristics or the otherareas of the system. As to the more detailed description of the GSMsystem, the GSM Recommendations, which are publicly available from theEuropean Standards Institute (ETSI), Sofia Antipolis, Valbonne, France(those in effect as of May 4, 1994), and the book "The GSM system forMobile Communications", M. Mouly & M. Pautet, Palaiseau, France, 1992,ISBN:2-9507190-0-7, are referred to.

A mobile exchange MSC handles the switching of inbound and outboundcalls. It performs tasks of a similar type as an exchange in a publicswitched telephone network (PSTN). In addition to these tasks, it alsoperforms functions characteristic of mobile call traffic only, such assubscriber location management, in co-operation with the subscriberregisters of the network. The GSM system comprises home locationregisters HLR and visitor location registers VLR as subscriberregisters. Mobile stations MS connect with the mobile exchange MSC bymeans of base station systems. A base station system BSS consists ofbase station controllers BSC and base stations BTS. One base stationcontroller BSC is used for controlling several base stations BTS. Forthe sake of clarity, FIG. 1 shows only one base station system, in whichsix base stations BTS1-BTS6 connect with the base station controllerBSC.

A signal in the GSM system consists of TDMA frames transmitted insuccession, each of which contains eight TDMA time slots, which are usedas logical channels. Information is transferred as radio-frequencybursts transmitted in the time slots. The logical channels includetraffic channels for the calls (speech or data) set up with the mobileradio stations MS located in a cell, and control channels for thesignalling carried out with the mobile radio stations MS located in acell. A speech connection or a data connection can be established on thetraffic channels. Typically, a separate connection adapter is requiredat both ends of a data connection for adapting the data connection toterminal equipments and/or other transmission connections/transmissionsystems. The connection adapter connected with a terminal equipment isusually referred to as a terminal adapter, and the common adapterlocated at the network end is referred to as a network adapter.

The hardware configuration for a telefax connection according to the GSMrecommendations is illustrated in FIG. 2. A telefax terminal isconnected by a normal two-wire modem connection to a special telefaxadapter 2, by which the signals of the telefax terminal are adapted to adata connection, which is established via a radio connection between amobile station MS and the base station system BSS to the mobile exchangeMSC and a network adapter IWF located therein, this network adaptercontaining a second telefax adapter 8A. This second telefax adapter 8Aadapts the above-mentioned data connection to a normal two-wire modemconnection for instance via a public switched telephone network PSTN 9to another telefax terminal B.

FIG. 3 illustrates the hardware configuration according to the GSMrecommendations for data transmission carried out by means of modems. Aradio terminal equipment A consists of a mobile station MS and a dataterminal equipment DTE1 connected thereto. A data connection isestablished from the radio terminal equipment via a radio connectionbetween the mobile station MS and the base station system BSS to themobile exchange MSC and there further to a network adapter IWF, whichcontains a data modem MOD1. The data modem MOD1 has a line interface(modem interface), which is connected to a normal two-wire line (2w),which in the exemplifying case is connected via a public switchedtelephone network PSTN 9 to a remote terminal equipment B, whichcomprises a remote modem MOD2 and a data terminal DTE2 connected to it.The data modem MOD1 of the network adapter and the remote data modem 10signal in the normal manner via the modem connection established betweenthem. As for the data terminal equipment DTE1, it controls the operationof the data modem MOD1 via the data connection and transmits data to thedata modem MOD1 and correspondingly receives it.

In the GSM system, each service may have its own directory number,MSISDN, Mobile Subscriber ISDN Number. For instance, a subscriber mayhave a number for a speech service, telefax service and modem service.This numbering is called the multi-numbering scheme. In themulti-numbering scheme, the calling subscriber must know which servicerelates to which directory number. The services of subscribers aredefined in the home location register HLR of a subscriber. In the homelocation register HLR, each directory number is associated with acorresponding service. In addition, a certain BCIE element, BearerCapability Information Element, is associated with an MSISDN number inthe home location register HLR, the BCIE element indicating the calltype and the network resources needed in the call. BCIE is described inthe GSM recommendation 04.08, version 4.5.0, pages 423-431.

In the future, it will be possible to use the ISDN BCIE in a GSM networktogether with the above-described GSM BCIE, this ISDN BCIE beingdescribed in the European Technical Standards Institute recommendationETS 300102-1/Q.931 (Bearer Capability IE), the version in effect as ofMay 4, 1994 being here referenced. This information element does notdirectly include call type information, wherefore the informationelements High Layer Compatibility (HLC) or Low Layer Compatibility (LLC)are used together with it, these elements being defined in the EuropeanTechnical Standards Institute recommendations ETS 300102-1/Q.931 HLC andETS 300102-1/Q.931 LLC. ISDN BCIE (and HLC and/or LLC), the versions ineffect as of May 4, 1994 being here referenced, may arrive at a mobileexchange in a call set-up message from a fixed network.

In the following, the set-up of a mobile station MS terminating call inthe GSM system will be described with reference to FIG. 4, the numberingfollowing the multi-numbering scheme. At stage 1, a call arrives to thefirst transit exchange GMSC of the network, this transit exchangetransmitting a routing information interrogation, message 2, to thesubscriber's home location register HLR, which is determined by thedirectory number MSISDN of the subscriber. The MSISDN number of thesubscriber (and possibly ISDN BCIE+HLC+LLC) is also transmitted in therouting information interrogation message 2. During location updating,information on the visitor location register VLR within the area ofwhich the subscriber is located has been updated to the subscriber'shome location register HLR. On the basis of this information, the homelocation register HLR transmits a mobile station roaming numberallocation request, message 3, to the visitor location register. TheBCIE relating to the MSISDN (or the ISDN BCIE arrived in message 2) isalso transmitted to the visitor location register VLR in the mobilestation roaming number allocation request, this BCIE indicating, forinstance, whether the type of the call is a data call or a speech call.The visitor location register VLR stores the BCIE it has received andallocates a mobile station roaming number MSRN. The visitor locationregister transmits the roaming number it has allocated, to the homelocation register HLR in a response message 5. The home locationregister HLR then transmits the roaming number in a message 6 further tothe exchange GMSC which had requested the routing information. Theroaming number space is defined in such a manner that the call is alwaysrouted to the exchange MSC the visitor location register VLR of whichhas allocated the roaming number. The transit exchange GMSC can thusroute the call forward on the basis of the roaming number bytransmitting an initial address message 7 to the mobile exchange MSCindicated by the roaming number.

After having received the initial address message 7, the exchange MSCnotices, in a roaming number analysis, that the call is terminating inthe area of that particular exchange and it is not intended to be routedfurther. The MSC thus requests next from its own visitor locationregister VLR for the information on the called subscriber for callset-up, message 8. In a normal situation, the visitor location registerVLR returns the necessary information in a response message 9, thisinformation including, for instance, the BCIE. If the MSC is capable ofproviding the data transmission resources required by the BCIE, callset-up signalling according to the GSM recommendations is carried outbetween the MSC and the MS, this signalling being illustrated witharrows 10 and 11. The call set-up proceeds in the above-mentioned mannerirrespective of whether what is involved is call set-up for speechtransmission or data transmission.

As stated earlier, the subscribers of mobile communication systems candefine different call forwarding functions. In unconditional callforwarding, a mobile terminating call is always forwarded to a givenforwarding number. In conditional forwarding, a mobile terminating callis forwarded to a determined call forwarding number when a certaincondition is fulfilled, for instance when the subscriber is busy, whenthe mobile station is not reachable, or when the mobile station isreached but the subscriber does not answer within a certain period oftime, for instance 30 seconds.

In the GSM system, call forwardings are set and activated basic servicegroup-specifically. When the multi-numbering scheme is used, a mobilesubscriber has a separate directory number MSISDN for each service. Thesubscriber can thus perform call forwardings service-specifically, ifthere are no other basic services in the same group. The subscriber can,for instance, forward speech calls to a secretary and telefax calls tothe office telefax number. Information on the call forwarding functionsactivated by the subscriber is stored permanently in the home locationregister HLR of the subscriber. In addition, information on at least theactivated conditional call forwardings is also given to the visitorlocation register VLR serving the subscriber and stored therein.

FIG. 5 illustrates the call-set-up procedure of a mobile station MSterminating call, with an associated conditional call forwarding in anexchange MSC serving the mobile station. In FIG. 5, call set-up messagesand operations 1, 2, 3, 4, 5, 6, 7 and 8 are entirely similar to theones described above in connection with FIG. 4. When the VLR receives asubscriber information request 8 from the exchange MSC in the case ofFIG. 5, the VLR checks the status of the mobile station MS in thesubscriber data and notices, for instance, that the mobile station isbusy. Next, the VLR checks in the subscriber data whether the mobilesubscriber has activated conditional call forwarding when the subscriberis busy. The VLR notices that the subscriber has such conditional callforwarding to a certain call forwarding number and transmits a responsemessage 9 to the exchange MSC, this message commanding the exchange toperform a call forwarding to the given number. The exchange MSC has apossibility to make an intermediate announcement to the callingsubscriber, in which announcement it is declared that the call isforwarded to the call forwarding number. The announcement may bechargeable to the calling subscriber or to the called subscriber. In theexemplifying case of FIG. 5, the exchange MSC makes an announcement tothe calling subscriber at stage 11, this announcement being recordedspeech, for instance taped or synthesized speech. The announcement istransmitted at stage 12 from the exchange MSC to the transit exchangeGMSC and from there further to the calling subscriber, stage 13.

Such an intermediate announcement is not problematic in connection witha speech call. However, intermediate announcements are problematic indata calls, in which the calling modem or telefax terminal waits for ananswer from the modem or telefax terminal at the other end only for apredetermines period, which is typically 10-40 seconds. If there is noreply within this period, the calling modem or telefax terminaldisconnects the call. The intermediate announcements described abovecause a delay to the call set-up, this delay possibly causing thetime-out of the calling modem or telefax terminal during callforwarding, and thus an unnecessary release of the call.

To obviate this problem, the visitor location register VLR is arranged,according to the invention, to also provide information in the responsemessage 10 of FIG. 5, in which are given a call forwarding command and acall forwarding number, as to whether the call is a data call or aspeech call. This information is preferably a BCIE element.Alternatively, the mobile exchange may also receive BCIE, HLC and LLC ina call set-up message (SETUP), if ISUP signalling is used between theexchanges. If an intermediate announcement is associated with the callforwarding, the exchange MSC is arranged to check the type of the callon the basis of the information provided and to prevent the intermediateannouncement from being switched to the calling subscriber if the callis a data call. If the call is a speech call, the intermediateannouncement is switched in a normal manner. This is a way of obviatingthe harmful delay due to intermediate announcements during data calls,such delay possibly causing the time-out of the calling modem or telefaxterminal.

FIG. 6 illustrates a case in which call forwarding is performed in atransit exchange GMSC. The transit exchange receives a mobileterminating call, stage 1, and performs a routing informationinterrogation to the subscriber's home location register HLR, stage 2,in the same manner as has been described hereinabove in connection withFIG. 4. The HLR notices that there is an unconditional call forwardingfor the called subscriber, or that the subscriber has disconnecteditself from the network and there is a call forwarding for thesubscriber in case of such a situation (stage 3). In the present-daysystems, the home location register HLR provides the transit exchangeGMSC with a notification of active call forwarding and a call forwardingnumber in a response message 4. The GMSC performs a call forwarding. Ifan intermediate announcement is associated with the call forwarding, theGMSC switches the intermediate announcement to the calling subscriber(stages 5 and 6) in the same manner as does the MSC in the case of theembodiment which has been described hereinabove with reference to FIG.5. A problematic delay as regards the calling modem or telefax terminalis thus produced again.

This is solved according to the invention in such a manner that the homelocation register HLR provides in the response message 4 information asto whether the call is a data call or a speech call, in addition toproviding the call forwarding number. This information is preferably aBCIE element.

Alternatively, the GMSC can use ISDN BCIE, HLC and/or LLC if it obtainsthese information elements in a call set-up message.

If an intermediate announcement is connected with the call forwarding,the GMSC is arranged to check the type of the call and to prevent theswitching of the intermediate announcement in the case of a data call.If the call is a speech call, the intermediate announcement is switchednormally. Also in this situation, the delay which is caused by theintermediate announcement and which is problematic as regards thecalling modem or telefax terminal is avoided.

FIG. 7 illustrates a way of applying the invention in a mobile exchangeMSC. For the sake of clarity, FIG. 7 shows of the exchange only aswitching matrix 83, call control 82, audio announcement unit 84,telefax adapter 8A and modem 8B, but, in practice, the MSC comprises asignificant number of different equipments. The switching matrix 83 maybe an analog or digital switching device, which selectively switchesspeech and data connections between the transmission lines 12 arrivingfrom the base station system BSS and the transmission lines 13 leavingthe mobile exchange. As an example of such digital exchanges, NokiaTelecommunications DX 220 MSC can be mentioned. A transit exchange GMSCcan also be a similar exchange.

Along with the switching matrix 83 are connected the telefax adapter 8Aand the modem 8B as network adapters. In the case of a data call, thecall control 82 controls the switching matrix 83 to switch a requiredadapter to the transmission connection in such a manner that theconnection according to FIG. 2 or 3 is produced. The network adaptersare not essential as regards the invention, however.

The audio announcement unit 84 is also connected to the switching matrix83. The call control 82 controls the switching matrix 83 and the audioannouncement unit 84 in such a manner that the unit 84 can be switched,if necessary, via the switching matrix 83 to make announcements to thecalling or called subscriber.

According to the invention, the call control 82 of the exchange, forinstance a computer, is arranged to perform the switching of audioannouncements during call forwarding in accordance with the flow diagramof FIG. 8. At stage 91, the call control 82 receives a call forwardingcommand, which contains a BCIE. At stage 92, the call control 82 checkswhether an intermediate announcement is connected with the callforwarding. If no intermediate announcement is connected with the callforwarding, the call control proceeds directly to stage 96 to performthe call forwarding. If an intermediate announcement is connected withthe call forwarding, the call control 82 checks the type of the call onthe basis of the BCIE (or ISDN BCIE+HLC+LLC) at stages 93 and 94. If thecall is not a data call, the call control 82 controls the switchingmatrix 83 and the audio announcement unit 84 to switch the intermediateannouncement to the calling subscriber at stage 95. If the call is adata call, the call control omits the intermediate announcement andproceeds directly past stage 95 to stage 96 to perform the callforwarding.

The figures and the description relating thereto are merely intended toillustrate the present invention. In its details, the invention may varywithin the spirit and scope of the appended claims.

I claim:
 1. An arrangement for carrying out call forwarding in a mobile communication system including mobile stations, mobile exchanges and subscriber databases for maintaining user data, such as location data and activated services, said arrangement comprising:a mobile exchange provided with means for making an intermediate announcement to a calling subscriber in connection with carrying out activated call forwarding; said mobile exchange being arranged to:receive a call to a called subscriber having a directory number; perform a routing information interrogation to a first database indicated by the directory number of the called subscriber; observe in the first database that call forwarding is activated for the called subscriber; start call forwarding; check on the basis of information obtained from the first database, or from a call set-up message, whether the call is a speech call or a data call; and prevent an intermediate announcement possible associated with call forwarding from being made if the call is a data call, but allowing the intermediate announcement to be made if the call is a speech call.
 2. A call forwarding method for a mobile terminating call, comprising the steps of:receiving a mobile terminating call from a calling subscriber to a called subscriber having a directory number, in a first exchange; performing a routing information interrogation to a first database indicated by the directory number of the called subscriber; performing a roaming number interrogation from the first database to a second database, within an area of which the called subscriber is located, thereby obtaining an allocated roaming number; transmitting the allocated roaming number from the second database to the first database, and further, to the first exchange; routing the call on the basis of the allocated roaming number from the first exchange to a second exchange, which serves the area of said second database; observing at the second exchange that the called subscriber is busy, is not reachable or does not answer; checking in the second database whether call forwarding is activated for the called subscriber and thereby determining call forwarding to be activated for the called subscriber; initiating the activated call forwarding, with which is possibly associated an intermediate announcement to the calling subscriber; checking on the basis of information obtained from the second database or from a call set-up message whether the call is a speech call or a data call; and preventing the intermediate announcement from being made to the calling subscriber in case of a data call, but allowing the intermediate announcement to be made to the calling subscriber in case of a speech call.
 3. The method according to claim 2, further comprising:transmitting said information as to whether said call is a speech call or a data call, from the second database to the second exchange, in response to performing a subscriber information interrogation by the second exchange.
 4. A call forwarding method for a mobile terminating call, comprising the steps of:receiving a mobile terminating call from a calling subscriber to a called subscriber having a directory number, in a first exchange; performing a routing information interrogation to a first database indicated by the directory number of the called subscriber; observing in the first database that call forwarding is activated for the called subscriber; starting the call forwarding; checking on the basis of information obtained from the first database as a result of said routing information interrogation, or from a call set-up message whether the call is a speech call or a data call; and preventing an intermediate announcement associated with the call forwarding from being made, if the call is a data call, but allowing the intermediate announcement to be made, if the call is a speech call.
 5. The method according to claim 4, further comprising:maintaining in the first database a dedicated directory number for each service available to the called subscriber and transmitting from the first database a notification of the call forwarding, a call forwarding number, and information concerning whether the call is a speech call or a data call, to the first exchange, when the first database receives the routing information interrogation for the directory number of the called subscriber and call forwarding is observed to be activated for the called subscriber.
 6. The method according to claim 3 or claim 5, wherein:said information transmitted as to whether said call is a speech call or a data call is transmitted as a Bearer Capability Information Element. 